Disneyland: the happiest place on Earth gave us some pretty bad news this month after a few of the park goers contracted a deadly respiratory infection called Legionnaire’s disease. The source of the outbreak was a cooling tower that spread the bacteria through mist. But the outbreak has left many people wondering – what is a cooling tower and how did it make those people sick?

The Outbreak:

The outbreak currently has confirmed cases of 15 people in the Anaheim area. These people became infected with Legionnaires’ disease. So far, 2 patients have died, but neither of them visited the park. Of the others, 11 of the 15 infected people had spent time at the park sometime in September. A Disney employee is also included among the 11 that were infected. All the 15 people are between the ages 52-94. 4 live in the Orange county but did not visit the theme park just like the 2 who died did not visit the park.

What is this deadly respiratory disease called Legionnaires?

Legionnaires is a severe form of atypical pneumonia. It is spread by a bacterium called Legionella Pneumophila found in both potable and non-potable water systems. Drinking water systems are the primary source of Legionella bacteria. It is not uncommon for people who are infected with Legionnaires to get hospitalized or undergo intensive treatments. In fact, most of the patients show some long-term effects from the disease. A study that was done on the survivors of a Legionella outbreak showed persistence of fatigue (75%), neurologic symptoms (66%) and neuromuscular symptoms (63%) as a long-term effect in patients.

Some symptoms of Legionnaires, include: cough, shortness of breath, diarrhea, vomiting, fever and chills, muscle pains, and headache. Incubation period of Legionnaires is 2-10 days.

People who are majorly at risk include

elderly,

those who have history of smoking,

Anyone suffering from chronic lung disease, and;

people who have poor immune function.

It is highly recommended that people who have pneumonia and those who have pneumonia and just travelled a while before should be tested for the disease.

Legionnaires disease is not contagious at all. The disease can be spread only through water and nothing else. Diagnosis of Legionnaires needs specialized laboratory tests which might not be available in all the hospitals. One of tests involves placing a culture media with furnish nutrients of the bacterium. Once the bacteria grow on the medium, it can be identified. Treatment of the infections includes antibiotics such as azithromycin, quinolones, etc.

What is a cooling tower?

A cooling tower is basically a heat rejection device that takes hot water out of systems (like an air conditioning unit), reduces the temperature of the water through direct contact between air and water via a specialized heat exchanger. It then, recycles cooled-off water back into the system.

This is how a cooling tower typically works:

Warm water from heat source such as air conditioning systems is piped onto the top of a cooling tower.

The water comes down in sprayed form and evaporates.

Large fans increase evaporation and helps in cooling the water.

This creates mist which is further emitted into the atmosphere from the top of the cooling tower and into the atmosphere.

How does a cooling tower spread the infection?

The major source of Legionella infection includes water distribution systems of any large building such as hotels or hospitals. Other sources include cooling towers, humidifiers, whirlpool spas, hot springs and mist machines. Air conditioners are not a source of the Legionnaires.

Cooling towers and water heaters form an ideal condition to grow the bacteria. The temperature of the water in most of the water systems that carry Legionella can come to Legionella bacteria growth appropriate temperature i.e. around 68-122 degrees Fahrenheit. The cooling tower moves the air through its recirculated water systems and emits a considerable amount of water vapor into the atmosphere. When these vapors that contains Legionella bacteria is inhaled by someone, they can get sick.

In fact, as reported by Wikipedia, French researchers found that the Legionella bacteria once travelled up to 6 km through air from a large contaminated cooling tower at a petrochemical plant in Pas de Calais, France. The outbreak was so huge that it killed 21 of the 86 infected people who had Legionella.

Studies have found Legionella to be present in 60-80% of cooling towers. Legionella is also prevalent in lakes, streams and ponds but the amount is so low that you are unlikely to get infected from these sources.

Maintenance of cooling tower to prevent Legionnaires:

The likelihood of Legionella infection by a cooling tower can be significantly reduced by following good engineering and water treatment practices. Taking good care while installing, operating and maintaining the air and water handling systems is crucial when it comes to preventing Legionella infection. Here are some other steps that all the cooling tower maintenance team should take.

All the cooling towers should be treated with dual biocide program that uses both oxidizing and non-oxidizing biocide during treatment.

Cooling towers and evaporative condensers should be treated, thoroughly cleaned and inspected at least twice a year to prevent any deadly outbreaks.

Algae and accumulated scale should be removed from cooling tower parts. All metal surfaces should be treated with a biocide and corroded parts should be replaced.

Units should be inspected monthly for any bacterial growth and drift eliminators should be inspected monthly.

All the cooling tower cleaning and maintenance should be done under careful supervision.

Monitoring for Legionella, however, remains controversial as presence of Legionella in a water system does not always mean that people who inhale the vapors will for sure contract the disease. But, scheduled monitoring at places such as hospitals is a must as people there are already suffering from diseases, have low immunity and can easily catch on any infections.

The local health department has already taken action and worked with Disney to shut down the 2 infected cooling towers that caused the outbreak. Not to forget the investigation is still ongoing, and the appropriate measures will be implemented soon.

1 Comments

Michael Ferrlen

Another potential treatment option for Legionella is a point-of-use UV disinfection system. The UV light irradiates the bacteria in the water before it is vaporized. Although point-of-use is difficult for UV lamps which have a long warm-up time, UV-LEDs offer more benefits for this application. A company that is working on UV LED systems are these guys: https://www.aquisense.com/water-treatment